Circuit for resetting an elevator safety chain

ABSTRACT

A circuit ( 34 ) for resetting a component ( 21 ) within an elevator safety chain ( 23 ). The reset circuit ( 24 ) comprises a first reset switch ( 31 ), a second reset switch ( 32 ) and a door contact ( 33 ). This first reset switch is mountable within an elevator shaft ( 2 ) and the second reset switch ( 32 ) is mountable outside the elevator. Preferably, the second reset switch ( 32 ) is hidden from members of the general public but is accessible to an elevator technician. The door contact ( 33 ) is mountable alongside the landing door ( 13 ). The first reset switch ( 31 ), the second reset switch ( 32 ) and the door contact ( 33 ) are arranged in series so that all must be closed to reset the component ( 21 ) whereby, upon activation, the first reset switch ( 31 ) remains closed for a first predetermined time period (Δt 1 ) after which it returns to its open state.

The present invention relates to elevators and, in particular, to acircuit for resetting an elevator safety chain after service technicianshave performed necessary maintenance or inspection operations within anassociated elevator shaft.

It is common practice within the elevator field for service techniciansto enter an elevator shaft to conduct periodic maintenance or inspectionoperations. The majority of the required operations can be conductedfrom either the shaft pit or alternatively throughout the shaft usingthe roof of an elevator car as a working platform. The frequency of thispractice has increased significantly in recent years due primarily tothe higher prevalence of machine-room-less installations within theindustry whereby elevator components which where traditionally housed ina dedicated, separate machine room are now fully incorporated within theelevator shaft.

Before any such work can be carried out within the shaft, localregulations such as the ASME A17.1-2000 safety code for the UnitedStated of America or the EN 81-1:1998 standard throughout Europestipulate that refuge or safety spaces must be created to protect anyservice technicians working in the pit or working from the roof of thecar. Obviously, the required refuge spaces can be permanentlyincorporated into the shaft, however, this solution extends the lengthof the shaft thereby occupying additionally commercial space which couldotherwise be utilized by the building owner for another purpose. Analternative solution is to create temporary refuge spaces.

U.S. Pat. No. 5,727,657 describes an elevator system wherein a temporaryrefuge space is created in the pit by pivoting a swivel buffer into thetravel path of the car to prevent the car from entering into the pit. Atemporary overhead refuge space can be established in a similar fashionby either pivoting a swivel buffer located in the pit into the travelpath of the counterweight, or by pivoting a swivel buffer arranged atthe shaft ceiling into the travel path of the car.

In order for a worker to be able to climb into the shaft pit, the car issent to a higher floor. The landing door at the lowermost floor can beunlatched and opened by rotating a bolt within the door frame with astandard triangular key. Furthermore, the rotation of the triangularbolt moves a latching switch into the detent or set position whereby asafety chain is interrupted and normal operation of the elevator isprohibited. When the safety chain is thus interrupted, the swivelbuffer, or preferably an opposed pair of the swivel buffers, tiltsautomatically into the travel path of the car and thus blocks the returnof the car to the lowermost floor and accordingly a temporary refugespace is created in the pit. Just before, or immediately after thetechnician climbs into the shaft pit, he can actuate the control off pitswitch, required by regulation, so that a multiple interruption of thesafety chain is achieved. The maintenance and checking work to beundertaken can now be performed with reduced risk.

After completion of the work in the pit, the pit switch is released andthe landing door is closed and latched. However, the elevator car stillis not yet ready for normal operation because the latching switch of thememory circuit is still in the set position interrupting the safetychain. In order to reset the latching switch and thereby the safetychain which in turn retracts the swivel buffer to the non-activeposition, the technician must activate a key switch at the elevatorcontrol which is located outside the elevator shaft preferably in themachine room or located beside or within a door frame at the uppermostfloor of the installation. Not only is this frustrating to thetechnician who has to mount the stairs from one extremity of thebuilding to the other but it is time consuming and therefore costly tothe building owner. Furthermore, during this procedure, there is acomplete lack of supervision at the landing door where the latchingswitch is in the set position so feasibly a person, for example anothertechnician, could open the landing door and enter the shaft, unknown tothe technician. Upon activation remote activation of the key switch, thesafety chain is re-established, the temporary refuge spaces areautomatically removed and the elevator resumes normal operation placingthe person in the shaft in an extremely dangerous situation.

An objective of the present invention is overcome the disadvantagesassociated with the prior art. This objective is achieved by providing acircuit for resetting a component within an elevator safety chain. Thereset circuit comprises a first reset switch and a door contact. Thefirst reset switch is mountable within an elevator shaft. The doorcontact is mountable alongside an elevator landing door. The first resetswitch and the door contact are arranged in series so that both must beclosed to reset the component whereby, upon activation, the first resetswitch remains closed for a first predetermined time period after whichit returns to its open state.

Accordingly, the invention permits the technician to reset the elevatorsafety chain directly from the landing by closing the landing door toactivate the door contact. The imposition of a first predetermined timeperiod within which the reset sequence must be completed firstlydramatically reduces the risk of inadvertently resetting of the safetychain and secondly forces the technician to make a conscious decision toreset the safety chain since any delay or interruption will extend thetime taken beyond the first predetermined time period in which case theentire procedure will have to be repeated until such time as iscompleted within the first predetermined time period.

The first reset switch can be accessible from the landing when thelanding door is open and is preferably mounted above the landing door.Thereby, the technician can activate the first reset switch by simplyreaching through the open landing door and into the shaft to activatethe first reset switch and according all stages of the reset sequenceare initiated by the technician while standing outside of the shaft.

Preferably, the first reset switch is an interval delay relay.

The first predetermined time period can be set to be marginally greaterthan the time taken for the landing door to close automatically. Uponactivation of the first reset switch, the technician need only withdrawhis hand from the shaft and release the landing door from its fully openposition. Such action should generally be completed within 2 s.Subsequently, the door will automatically move under bias to its closedposition which, for example, may take 6 s. Accordingly, in thissituation, the first predetermined time period should be set to 8 s.Naturally the first switch can be positioned such that the door need notbe fully opened to activate the switch in which case the firstpredetermined time period can be reduced preferably to less than fiveseconds.

To improve security and longevity, the circuit can further comprise asecond reset switch mountable external to the shaft and arranged inseries with the first reset switch and the door contact. Thisnecessarily increases the reset sequence and consequently the firstpredetermined time limit should be increased but should preferably beless than ten seconds. Preferably, the second reset switch remainsclosed for a second predetermined time period after which it returns toits open state and more preferably it is an interval delay relay. Thesecond predetermined time period should be set to reflect the operatingparameters of the component within the elevator safety chain. Inparticular, the second time must be sufficiently long to enable thereset of the elevator safety chain component, however should not be soexcessive as to damage or burn out the component.

The invention also provides an elevator comprising a car verticallydisplaceable within a shaft, a plurality of landing doors and a safetychain. In use, if one of the landing doors is opened without thesimultaneous presence of the car at that level, the safety chain isbroken and the car is prevented from further travel. The elevatorfurther comprises a reset circuit as described above to reset the safetychain. The first reset switch can be mounted to a door frame andpreferably to either to an upper transverse section or a side portion ofthe door frame. In the preferred embodiment, the elevator safety chaincomponent is a bi-stable safety switch which interrupts the safety chainwhen the landing door is opened without the simultaneous presence of thecar at that level.

The present invention is hereinafter described by way of specificexamples with reference to the accompanying drawings in which:

FIG. 1 is a general schematic of an elevator incorporating a resetcircuit according to the present invention;

FIG. 2 is a perspective view of the landing door at the lowermost floorof FIG. 1 as viewed from the front or hall side thereof;

FIG. 3 is an enlarged fragmentary view of the unlatching and releasedevice shown in the FIG. 2 before actuation;

FIG. 4 is a view similar to FIG. 3 showing the unlatching and releasedevice upon actuation;

FIG. 5 is a view similar to the FIG. 4 showing the unlatching andrelease device after the actuation and before resetting;

FIG. 6 is a schematic showing a reset circuit according to the preferredembodiment of the present invention;

FIG. 7 a is a graphical representation of the operating conditions ofthe first interval delay relay of FIG. 6;

FIG. 7 b is a graphical representation of the operating conditions ofthe door contact of FIG. 6;

FIG. 7 c is a graphical representation of the operating conditions ofthe second interval delay relay of FIG. 6; and

FIG. 7 d is a graphical representation of the operating conditions ofthe elevator safety chain.

FIG. 1 shows an elevator arranged within a building. The elevatorcomprises a car 1 and a counterweight 5 which are supported on a loadcarrying element 3 by pulleys 6. The load carrying element 3 is fixed ateither end and is driven by a traction sheave 4 to vertically displacethe car 1 and the counterweight 5 in opposite directions alongassociated guide rails (not shown) mounted within a shaft 2. When thecar 1 is level with any landing, passengers can enter or exit the car 1through the respective landing door 13 a, 13 b, 13 c, 13 d.

When a service technician is required to enter the elevator shaft 2, forexample to conduct periodic maintenance or inspection operations, bolts11 are extended from the bottom of the car 1. As shown in specificallyin FIG. 1, the car 1 is prevented from moving along its normal travelpath into a pit 7 of the elevator shaft 2 through the engagement of theextended bolts 11 with a first set of buffers or brackets 9 secured tothe guide rails or mounted to the shaft walls, thereby creating atemporary refuge space in the pit 7. Similarly, a temporary overheadrefuge space is created between a shaft ceiling 8 and the roof of thecar 1 through the engagement of the extended bolts 11 with a second setof buffers or brackets 10 mounted at a higher position within the shaft2. Such arrangements are further described in EP-A1-1602615 and U.S.Pat. No. 7,258,202. After the required refuge spaces have been created,the service technician can safely enter the pit 7 through the lowermostlanding door 13 a.

As shown in FIG. 2 the lowermost landing door 13 a comprises a fastpanel 14 a and a slow panel 14 b which telescope past each other to openand close the entrance to the shaft 2. The door 13 a is bound at thebottom by a sill 15 and is surrounded by a door frame 19 consisting oftwo side portions and an upper transverse section 19 a. A reset pushbutton 30 is mounted inside the shaft 3 on the upper transverse section19 a of the door frame 19 and is accessible to a technician standing onthe sill 15 through the open landing door 13 a.

A triangular bolt 18 and a small hole 19 b are provided in a sideportion of the door frame 19 and are normally covered by screw lids (notshown) or a slide (not shown). In order to gain access to the pit 7, theservice technician rotates the bolt 18 using a standardized triangularkey. This action not only unlatches and permits the technician tomanually open the door 13 a, but simultaneously sets a memory circuitand interrupts an elevator safety chain 23, as illustrated in the FIGS.3, 4 and 5. With the landing door 13 a open, the technician can reachinto the shaft 2 and actuate a pit switch 17, required by regulation inthe pit 7, to ensure that a multiple interruption of the safety chain 23is achieved. The maintenance and inspection work to be undertaken cannow be performed with reduced risk.

The bolt 18 and the memory circuit are components of an unlatching andrelease device 26 as shown in FIGS. 3, 4 and 5. The memory circuitincludes a bi-stable, safety switch 21 and a resetting element in theform of an electromagnet 20 which forces the safety switch 21 to aninitial setting as shown in the FIG. 3. The switch 21 has a first pairof contacts connected to a pair of signal lines 21 a and 21 b which, inthe initial setting, are bridged by a switch element 21 c. The signallines 21 a and 21 b and the safety switch 21 form a branch of theelevator safety chain 23.

The actuation of the memory circuit takes place by way of a switchingcam 22 coupled to the triangular bolt 18. When the triangular bolt 18 isrotated through a predetermined angle, a switch actuator rod 21 d of thesafety switch 21 is moved by the rotated cam 22 into a detent setting orset position as shown in the FIG. 4 and remains in this setting afterthe release of the triangular bolt 18. The actuator rod 21 d is coupledto the switch element 21 c which is moved away from the first set ofswitch contacts, thereby interrupting the safety chain 23, to bridge asecond set of switch contacts. Upon release, the bolt 18 is rotated by aspring force to the initial position as shown in the FIG. 5. However,the switch element 21 c and the actuator rod 21 d remain in the detentor set position. As discussed above, activation of the pit switch 17further interrupts the elevator safety chain 23 as shown in FIG. 5.

Once the required work has been completed in the shaft 2, the techniciancan reset the pit switch 17 whereby the unlatching and release device 26reverts back to the condition as shown in FIG. 4. However, in thiscondition the elevator is prevented from returning to normal servicebecause the safety chain 23 is still interrupted by the bi-stable,safety switch 21 which remains at the detent setting or set position.

A circuit 34 for resetting the safety switch 21 is shown in FIG. 6.After resetting the pit switch 17, the technician, while standing on thesill 15, presses the reset push button 30 mounted inside the shaft 2 onthe upper transverse section 19 a of the door frame 19 through the openlanding door 13 a. This in turn activates a first interval delay relay31 at time t₀ which remains closed for a first predetermined time periodΔt₁ after which it returns to its open state as shown in FIG. 7 a(wherein logic 1 represents the relay 31 in a closed condition and logic0 represents the relay 31 in an open condition). The first time periodΔt₁ strictly defines the timeframe in which all of the following actionsmust be taken in order to reset the safety switch 21.

Next, at time t₁, the technician closes the door 13 a and a door contact33 closes upon the reset circuit 34, as shown in FIG. 7 b, confirmingthat the door 13 a has been closed and locked.

Finally, at time t₂, the technician activates a second interval delayrelay 32 by inserting a small screw driver 16 through the hole 19 b inthe landing door frame 19. The second interval delay relay 32 remainsclosed for a second predetermined time period Δt₂ as shown in FIG. 7 c.

So long as the first interval delay relay 31, the door contact 33 andthe second interval delay relay 32 are simultaneously closed onto thereset circuit 34 for the second time period Δt₂, sufficient energy isprovided to the electromagnet 20 at time t₃ through power supply lines20 a and 20 b to shift the switch element 21 c and the actuator rod 21 dto the left and back to the initial position shown in the FIG. 3.Accordingly, the pit switch 17 and the switch element 21 c complete thesafety chain and the elevator automatically returns to normal operationas represented in FIG. 7 d. The second time period Δt₂ must besufficiently long to enable the energized electromagnet 20 to reset thesafety switch 21, however should not be so excessive as to damage orburn out the electromagnet 20. In the present embodiment the acceptablerange is between 0.2 s and 0.5 s and the second time period Δt₂ is setto 0.3 s.

Although the invention has been described above specifically forarrangement at the lowermost landing door 13 a, it will be appreciatedthat the invention can equally be applied to any landing door throughwhich the service technician gains access to the shaft 2 in order tocarry out his work. For example, to gain access to the roof of the car1, a technician will generally call the car 1 to one of the upperfloors. Upon arrival, he will enter the car 1, register a call for alower floor and immediately leave the car 1. Once the landing doorsubsequently closes, the car 1 starts to descend and a short timethereafter the technician will unlatch the landing door by rotating anassociated triangular bolt 18. As before, such action willsimultaneously set a memory circuit, interrupt the elevator safety chain23 and thereby stop the car 1. Upon manually opening the landing door,the roof of the car should be easily accessible. However, beforemounting the roof, the technician must press a stop switch (equivalentto the pit switch 17) provided on the car roof to ensure multipleinterruption of the safety chain 23. Thereafter, using a car mountedinspection control device, the technician can drive the car atinspection speed along the restricted travel path (defined by the firstset buffers 9 and the second set of buffers 10 as shown in FIG. 1) tocarry out the required maintenance and inspection operations from thetop of the car 1. The triangular bolt 18, the memory circuit, the safetychain branch 23 and the resetting circuit 34 used for this upper landingdoor are identical to, and operate in exactly the same way, as thoseshown and described in relation to the lowermost landing door 13 a withthe sole exception that the car mounted stop switch replaces the pitswitch 17.

In an alternative embodiment, the second switch 32 can be a conventionalbi-stable switch without interval delay action.

Although the preferred embodiment requires a three stage sequence(activation of the first interval delay relay 31, closing door 13 a toclose the door contact 33 and activation of the second interval delayrelay 32) to reset the safety switch 21 and thereby the safety chain 23,it will be appreciated that the invention can be simplified whilemaintaining many of its advantages by eliminating the second intervaldelay relay 32 and the related third stage of the resetting sequence.

The first predetermined time period Δt₁, established by activating thefirst interval delay relay 31, should be sufficiently short so thatsafety switch 21 and safety chain 23 will not be reset if there is evena slight delay or interruption to the reset sequence. In such a case,the sequence will need to be repeated until it is completed within thetime period Δt₁. For the three stage reset sequence used in thepreferred embodiment, the first predetermined time period Δt₁ should beless than 10 s. For the two stage sequence described in the paragraphimmediately above, the first predetermined time period Δt₁ should beonly marginally greater than the time it takes for the landing door toclose and preferably less than 5 s.

In an alternative embodiment, the reset push button 30 can be mountedone of the side portions of the door frame 19 within the shaft 2 insteadof on the upper transverse section 19 a.

The invention claimed is:
 1. A circuit for resetting a component withinan elevator safety chain comprising: a first reset switch mountablewithin an elevator shaft; and a door contact mountable alongside alanding door; wherein the first reset switch and the door contact arearranged in series so that both must be closed to reset the component,and configured such that upon activation, the first reset switch remainsclosed for a first predetermined time period after which the first resetswitch returns to an open state.
 2. A circuit according to claim 1,wherein the first reset switch is accessible from a landing when thelanding door is open.
 3. A circuit according to claim 1, wherein thefirst reset switch is mountable above the landing door.
 4. A circuitaccording to claim 1, wherein the first reset switch is an intervaldelay relay.
 5. A circuit according to claim 1, wherein the firstpredetermined time period is greater than a time taken for the landingdoor to close automatically.
 6. A circuit according to claim 1, whereinthe first predetermined time period is less than five seconds.
 7. Acircuit according to claim 1 further comprising a second reset switchmountable external to the elevator shaft and arranged in series with thefirst reset switch and the door contact.
 8. A circuit according to claim1, wherein the first predetermined time period is less than ten seconds.9. An elevator comprising: a car vertically displaceable within a shaft,a plurality of landing doors; a safety chain; and a reset circuit inaccordance with claim 1, wherein, in response to opening one of theplurality of landing doors at a particular level while the car is notpresent at that level, the safety chain is broken and the car isprevented from further travel.
 10. An elevator according to claim 9,wherein the first reset switch is mounted to a door frame.